A spectroscopic search for White Dwarf companions to 101 nearby M dwarfs

Recent studies of the stellar population in the solar neighborhood (<20 pc) suggest that there are undetected white dwarfs (WDs) in multiple systems with main sequence companions. Detecting these hidden stars and obtaining a more complete census of nearby WDs is important for our understanding of binary and galactic evolution, as well as the study of explosive phenomena. In an attempt to uncover these hidden WDs, we present intermediate resolution spectroscopy over the wavelength range 3000-25000 \AA\ of 101 nearby M dwarfs (dMs), observed with the Very Large Telescope X-Shooter spectrograph. For each star we search for a hot component superimposed on the dM spectrum. X-Shooter has excellent blue sensitivity and thus can reveal a faint hot WD despite the brightness of its red companion. Visual examination shows no clear evidence of a WD in any of the spectra. We place upper limits on the effective temperatures of WDs that may still be hiding by fitting dM templates to the spectra, and modeling WD spectra. On average our survey is sensitive to WDs hotter than about 5300 K. This suggests that the frequency of WD companions of T<5300 K with separation of order <50 AU among the local dM population is <3% at the 95% confidence level. The reduced spectra are made available on via WISeREP repository.Comment: 41 pages, 105 figures, 2 tables. Submitted to AAS journal

THE USE OF RULE-BASED EXPERT SYSTEMS TO INVESTIGATE THE EFFECTS OF EXPERIENCE ON AUDIT JUDGMENTS

Rule-based expert systems (RBES) are currently the focus of a great deal of research interest. Most of that work, however, has concentrated on the development of such systems. There has not been much analysis of the resulting RBES. This paper examines two RBESs designed to make audit judgments. The knowledge bases of the initial prototype versions of each system contain the rules used by novice auditors. Each system was refined by having experienced auditors use the system to make the audit judgments for actual clients. The rules contained in the refined versions of each RBES thus represent the knowledge used by an experienced auditor to make a particular audit judgment. The effects of experience are then examined by comparing the rules in the initial prototype knowledge base to those contained in the refined version of each system. Experience appears to provide the capability to deal with exceptions to general rules and expectations

Combinatorial Contracts Beyond Gross Substitutes

We study the combinatorial contracting problem of D\"utting et al. [FOCS '21], in which a principal seeks to incentivize an agent to take a set of costly actions. In their model, there is a binary outcome (the agent can succeed or fail), and the success probability and the costs depend on the set of actions taken. The optimal contract is linear, paying the agent an $\alpha$ fraction of the reward. For gross substitutes (GS) rewards and additive costs, they give a poly-time algorithm for finding the optimal contract. They use the properties of GS functions to argue that there are poly-many "critical values" of $\alpha$, and that one can iterate through all of them efficiently in order to find the optimal contract. In this work we study to which extent GS rewards and additive costs constitute a tractability frontier for combinatorial contracts. We present an algorithm that for any rewards and costs, enumerates all critical values, with poly-many demand queries (in the number of critical values). This implies the tractability of the optimal contract for any setting with poly-many critical values and efficient demand oracle. A direct corollary is a poly-time algorithm for the optimal contract in settings with supermodular rewards and submodular costs. We also study a natural class of matching-based instances with XOS rewards and additive costs. While the demand problem for this setting is tractable, we show that it admits an exponential number of critical values. On the positive side, we present (pseudo-) polynomial-time algorithms for two natural special cases of this setting. Our work unveils a profound connection to sensitivity analysis, and designates matching-based instances as a crucial focal point for gaining a deeper understanding of combinatorial contract settings.Comment: 22 pages, 3 figure

The influence of a good relationship between the internal audit and information security functions on information security outcomes

Given the increasing financial impact of cybercrime, it has become critical for companies to manage information security risk. The practitioner literature has long argued that the internal audit function (IAF) can play an important role both in providing assurance with respect to information security and in generating insights about how to improve the organization\u27s information security. Nevertheless, there is scant empirical evidence to support this belief. Using a unique data set, this study examines how the quality of the relationship between the internal audit and the information security functions affects objective measures of the overall effectiveness of an organization\u27s information security efforts. The quality of this relationship has a positive effect on the number of reported internal control weaknesses and incidents of noncompliance, as well as on the numbers of security incidents detected, both before and after they caused material harm to the organization. In addition, we find that higher levels of management support for information security and having the chief information security officer (CISO) report independently of the IT function have a positive effect on the quality of the relationship between the internal audit and information security functions

Effects of rehydration nutrients on H2S metabolism and formation of volatile sulfur compounds by the wine yeast VL3

In winemaking, nutrient supplementation is a common practice for optimising fermentation and producing quality wine. Nutritionally suboptimal grape juices are often enriched with nutrients in order to manipulate the production of yeast aroma compounds. Nutrients are also added to active dry yeast (ADY) rehydration media to enhance subsequent fermentation performance. In this study we demonstrate that nutrient supplementation at rehydration also has a significant effect on the formation of volatile sulfur compounds during wine fermentations. The concentration of the 'fruity' aroma compounds, the polyfunctional thiols 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl acetate (3MHA), was increased while the concentration of the 'rotten egg' aroma compound, hydrogen sulfide (H2S), was decreased. Nutrient supplementation of the rehydration media also changed the kinetics of H2S production during fermentation by advancing onset of H2S production. Microarray analysis revealed that this was not due to expression changes within the sulfate assimilation pathway, which is known to be a major contributor to H2S production. To gain insight into possible mechanisms responsible for this effect, a component of the rehydration nutrient mix, the tri-peptide glutathione (GSH) was added at rehydration and studied for its subsequent effects on H2S formation. GSH was found to be taken up during rehydration and to act as a source for H2S during the following fermentation. These findings represent a potential approach for managing sulfur aroma production through the use of rehydration nutrients

The Type Ia Supernova Rate in Redshift 0.5--0.9 Galaxy Clusters

Supernova (SN) rates are potentially powerful diagnostics of metal enrichment and SN physics, particularly in galaxy clusters with their deep, metal-retaining potentials and relatively simple star-formation histories. We have carried out a survey for supernovae (SNe) in galaxy clusters, at a redshift range 0.5<z<0.9, using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. We reimaged a sample of 15 clusters that were previously imaged by ACS, thus obtaining two to three epochs per cluster, in which we discovered five likely cluster SNe, six possible cluster SNe Ia, two hostless SN candidates, and several background and foreground events. Keck spectra of the host galaxies were obtained to establish cluster membership. We conducted detailed efficiency simulations, and measured the stellar luminosities of the clusters using Subaru images. We derive a cluster SN rate of 0.35 SNuB +0.17/-0.12 (statistical) \pm0.13 (classification) \pm0.01 (systematic) [where SNuB = SNe (100 yr 10^10 L_B_sun)^-1] and 0.112 SNuM +0.055/-0.039 (statistical) \pm0.042 (classification) \pm0.005 (systematic) [where SNuM = SNe (100 yr 10^10 M_sun)^-1]. As in previous measurements of cluster SN rates, the uncertainties are dominated by small-number statistics. The SN rate in this redshift bin is consistent with the SN rate in clusters at lower redshifts (to within the uncertainties), and shows that there is, at most, only a slight increase of cluster SN rate with increasing redshift. The low and fairly constant SN Ia rate out to z~1 implies that the bulk of the iron mass in clusters was already in place by z~1. The recently observed doubling of iron abundances in the intracluster medium between z=1 and 0, if real, is likely the result of redistribution of existing iron, rather than new production of iron.Comment: Accepted to ApJ. Full resolution version available at http://kicp.uchicago.edu/~kerens/HSTclusterSNe

The Role of Accounting and Professional Associations in IT Security Auditing

Information Systems Security is a critical area of inquiry and scholarship in our field, yet relatively little is known about the process by which scholars and professionals become certified as security experts for purposes of assessing the quality of information security implementations. The Information Systems Audit and Control Association (ISACA.org) is the professional association that serves as a bridge between the expertise area from which auditing skills are delivered and assessed and the areas in which information systems security is developed and delivered, effectively bridging the practices of accounting and IT Security. Individuals skilled in accounting, such as graduates from combined Accounting/Information Systems departments in business schools are naturally oriented to such industry groups and certifications, but the mainstream IT practice and literature is not. This panel will serve to brief IT Security researchers interested in the process of auditing on the values and procedures of the certification process with implications for understanding corporate IT Security performance as a function of auditing expertise represented at the highest levels of organizational decision making

Eighth Major Clade for Hepatitis Delta Virus

Hepatitis delta virus is the only representative of the Deltavirus genus, which consists of 7 differentiated major clades. In this study, an eighth clade was identified from 3 distinct strains. Deltavirus genetic variability should be considered for diagnostic purposes. Clinical consequences of the diversity have yet to be evaluated

Spectropolarimetry of SN 2011dh in M51: geometric insights on a Type IIb supernova progenitor and explosion

We present seven epochs of spectropolarimetry of the Type IIb supernova (SN) 2011dh in M51, spanning 86 days of its evolution. The first epoch was obtained 9 days after the explosion, when the photosphere was still in the depleted hydrogen layer of the stripped-envelope progenitor. Continuum polarization is securely detected at the level of P~0.5% through day 14 and appears to diminish by day 30, which is different from the prevailing trends suggested by studies of other core-collapse SNe. Time-variable modulations in P and position angle are detected across P-Cygni line features. H-alpha and HeI polarization peak after 30 days and exhibit position angles roughly aligned with the earlier continuum, while OI and CaII appear to be geometrically distinct. We discuss several possibilities to explain the evolution of the continuum and line polarization, including the potential effects of a tidally deformed progenitor star, aspherical radioactive heating by fast-rising plumes of Ni-56 from the core, oblique shock breakout, or scattering by circumstellar material. While these possibilities are plausible and guided by theoretical expectations, they are not unique solutions to the data. The construction of more detailed hydrodynamic and radiative-transfer models that incorporate complex aspherical geometries will be required to further elucidate the nature of the polarized radiation from SN 2011dh and other Type IIb supernovae.Comment: Post-proof edit. Accepted to MNRAS 2015 Aug 1